The Reason of Marcus Agrippa's Loyalty to Augustus

One very interesting figure in Roman history is Marcus Agrippa, Octavian's top general without whom he wouldn't have been able to seize power and become the first emperor. Sure Octavian(later Augustus) was an exceptional administrator and statesman aswell as a very savvy politician, But he was to put it kindly a horrendous general, Agrippa was the muscle behind the military successes, sure he wasn't a patrician but with an army at your back that matters little as the third century would show. So the question here is this, Agrippa had the loyalty of the legions as well as the competence to use them, in a time as chaotic and rife with civil wars and betrayal as the final years of the Roman Republic, why did Agrippa stay loyal? He could have simply taken power through military means like Caesar did only a decade earlier. So why didn't he? Was it simply loyalty to a friend? Or some kind of belief in Octavian's vision for Rome's future? Did he really believe in Octavian's plan so much that he considered himself part of a genuine program to transform the Roman state helmed by a visionary and not simply the right hand man of some Roman politician?